Carburetor



March 22, 1960 A. F. BRAUN CARBURETOR Filed Dec. 19, 1957 IN I 'E N TO R. Wa 0i zgmzzz I 7, {M i I ATTORNEY nited States Patent CARBURETOR Adolph F. Braun, Pittsford, N.Y., msignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application December 19, 1957, Serial No. 703,889

4 Claims. (Cl. 261-41) The present invention relates to a new and improved carburetor of the compound or plural induction passage type.

Present day carburetors are faced with a size dilemma posed by two increasing but opposed requirements. With the ever increasing size and power of engines it is necessary that the capacity and more particularly the breathing capacity of carburetors be increased to provide sufficient combustible mixture to satisfy the needs of the engine. The natural result of this demand has been to increase carburetor size. In general this has been achieved by utilizing compound type carburetors which utilize a plurality of induction passages and which are in effect a plurality of carburetors combined into one body in such a way that only part of the carburetor is used under low power conditions and the entire carburetor utilized under high power conditions.

However, along with the demand for increased carburetor capacity and the concomitant increase in carburetor size comes the equally exacting requirement imposed by lower vehicle profiles that at least the vertical displacement of a carburetor be continually reduced in order to facilitate lower hood lines. These conflicting demands on the carburetor industry present a serious dilemma.

The present invention relates to a new carburetordesign in which it is possible to reduce the vertical displacement of a carburetor without correspondingly reducing its capacity. The problem of reducing carburetor profile or vertical displacement is particularly aggravated with those carburetors which utilize air actuated auxiliary throttles in combination with manual throttles in the secondary induction passages. Carburetors using the air flow actuated throttles, as shown in copending application Serial No. 257,578'Braun, filed November 21, 1951, now abandoned, are considered highly desirable because of the increased accuracy of supplying combustible mixture in the secondary induction passages in accordance with engine demand. However, such auxiliary valve type carburetors have traditionally paid a slight penalty of a higher carburetor profile due to the addition of an extra throttle valve.

In the present carburetor, the penalty previously paid in terms of higher carburetor profile is eliminated with the discovery that it is possible to construct the primary and secondary induction passage main venturis at relatively difierent heights from a given horizontal plane.

In other words, it has been found possible to displace the secondary passage main venturi axially upwardly in relation to the corresponding venturi in the primary induction passage. It has been further discovered that the secondary main venturi may be axially displaced from the primary main venturi a distance substantially equal to that previously required to accommodate the air actuated throttle. In this way a carburetor utilizing an air actuated secondary throttle valve may be constructed without an added height penalty relative to a carburetor eliminating such a valve.

"ice

By the differential spacing of the primary and sec ondary main venturis it is now found that the length of the primary induction passage determines the overall displacement of the carburetor whereas previously, with carburetors utilizing air actuated secondary throttles, it was found that the length of the secondary induction passage determined the overall height of the carburetor.

In addition to reducing the carburetor profile by disposing the secondary venturi above the primary venturi, it has also been found that no loss in the performance of the carburetor is realized by the change.

Other objects and advantages of the present invention will be apparent from a perusal of the detailed description which follows.

The drawing is a partially sectioned elevational view of a carburetor embodying the subject invention.

In the drawing, a carburetor is indicated generally at 10 and is comprised of three casing members including the throttle body casing 11, a float bowl casing 13 and a cover casing 15. Primary and secondary mixture or induction passages 12 and 14 are formed in casings 11,

13 and 15. Mechanically coupled throttle valves 16 and 18 are respectively disposed in the primary and secondary induction passages 12 and 14. These throttles are preferably sequentially operating in the manner shown and described in Patent 2,771,282 Olson et al. Briefly, the throttles are constructed and arranged so that the primary throttle 16 will open to a given amount, e.g. 40%, before the secondary throttle 18 will begin to open.

This type of mechanically coupled sequentially operating throttles provides a control of carburetor operation which is indicative of operator demand. However, with this type of operation it is possible for the operator to open the throttles to provide air flow in excess of the needs of the engine. The result of this over-opening of the throttles is to cause 'afl leaning out of the combustible charge which inevitably'results in a fall-off of power. To prevent this occurrence an additional or auxiliary throttle 20 is disposed in the secondary induction passage 14 anteriorly of the secondary throttle 18. The auxiliary or air actuated throttle 20 cooperates with the mechanical throttle 18 in the manner shown and described in copending application Serial No. 257,578 Braun, filed November 21, 1951.

Thus, irrespective of the degree of opening of throttle 18, the air flow through the secondary induction passage 14 will be determined by the pressure drop across the air actuated throttle 20.

' The primary and secondary induction passages 12 and 14 respectively include fuel clusters indicated gen,- erally at 22 and 24-having booster venturis 26 and 28 which induce fuel to flow through the clusters at a rate proportional to air flow. The fuel clusters 22 and 24 and associated fuel passages are formed in substantially the same manner as in the aforenoted Olson patent. The primary and secondary cluster fuel passages are of substantially the same sizes and flow capacities. The clusters are located in the same relative positions with respect to their associated induction passages save for the vertical displacement of the secondary cluster 24, infra. The secondary induction passage fuel cluster 24 includes a tube portion 30 depending therefrom and projecting through an opening 32 in the auxiliary air throttle 20 when the latter is closed. As described in copending application Serial No. 675,721 Olson, filed August 1, 1957, now Patent No. 2,899,184 dated August 11, 1959, tube 30 is subjected to manifold depression as soon as the secondary throttle 18 is open which insures the prompt flow of fuel through the secondary fuel cluster as soon as the auxiliary throttle 20 begins to open.

The primary induction passage includes a choke valve 34 adapted to be operated by an automatic choke mechr V. V 2,929,618

' anisrn ofthe type shownin Patent 2,705,484 Jorgensen.

A main venturi 36 is provided in-the primary induction passage intermediate the throttle and choke valves 16 and 34. Ventu'ri 36 cooperates with the secondary or boosterventuri 26 in the normal manner to induce the flow'of fuel through the fuel cluster 22 in proportion to the quantity of air flow-through the induction passage,

supra. V

' A similarly functioning venturi 38 isprovided in the secondary induction passage 14. It is to be noted :that

the secondary venturi '38 is formed in float bowl casing 13 in axially upwardly or vertically'spaced relation with tional placementjof the venturi-in horizontal alignment above the throttle body as shown'in the 'aforenoted copending Braun application.

' Historically, the. addition lo'f 'the auxiliary type air actuated throttle, suchxas 20, has resulted in an increase in vertical displacement of the'carburetor so as to insure ondarylhrottle and the air actuated throttle; The tra;

' ditional reason for the alignment ofthe primary and secondary venturis at an equal distance above some horizontal reference plane, such as the. throttle body or the intake manifold, was in the belief that such disposition was necessary to insure proper functioning of the cara the throttle valve,and a main venturi formed in said secondary induction passage, said secondary induction passage main venturi being disposed vertically above said primary venturi. j

2. A charge forming device for an internal combustion engine comprising adjacently disposed vertically ex- Tespect to the primary venturi- 36. 'This disposition of a the secondary main venturi is in contrast to the tradiwith the primary ,ventuii and disposed equal distances a non-interfering operation between the manual secburetor; It is found, however, that by displacingfthe i venturis as'show'n there was no demonstrable 'diiierence In the present-cap buretor the primary main venturi 36 is located a distance,

'in'the operation of the carburetor.

a abovethe base'of throttle body 11 whereassecondary venturi 38 is located a greaterdistance b. The height differential cf between the venturis then represents the height previously added to accommodate an air throttle. such' as 20. From the drawing it willibe appreciated that .percentagewise the saving or reduction in carburetor height, represented by distance fc, is considerable prob- 1 ably being in the nature of 15-20%;

As already noted the ability to be able to realize such an appreciable saving in the vertical displacement of a carburetor greatly facilitates the reduction of a vehicle f hood line without atthe. same time reducing the overall capacity of the carburetor.

Iclaimi. '1. A charge forming device for an internal combustion engine comprising adjacently disposed vertically extendiing primary and secondary induction passages,

'rnanually controlled throttlevalves respectively disposed in said primary. and secondary induction passages, an air flow actuated auxiliary throttle valve disposed in said secondary induction passage anteriorly of said mechaniformed in said primary induction passage anteriorly of cally operating secondary throttle valve, a main venturi tending primary and secondary induction passages, sequentially operating manual throttles respectively disposed in said primary and. secondary induction :passages,

said sequentially operating throttles beingsubstantially horizontally aligned, an auxiliary air operated throttle disposed in said secondary induction passage anteriorly 'of the secondary sequentially operating throttle, amain venturi formed in said primary .inductionjpassage anteriorly of the. associated throttle valve, and a main venturi formed in said secondary induction passage anteriorly ofsaid auxiliary throttle, said secondary main venturi being disposed vertically above said primary venturi. 3. A carburetor forqan internal combustion engine comprising a throttle body casing, a float bowl casing, a

cover casing, adjacently disposed vertically extending primary and secondary "induction passages formed through said casings, sequentially. operating manual throbtles respectively disposed in ,said throttle body for controlling cflow throughsaid primary. and secondary induction passages, said sequenta illy op'eratingthrottles being substantially horizontally aligned, an auxiliary air flow operated throttle disposed insaid secondaryinduction passage anteriorly of the secondary sequentially operating throttle, main venturis respectively formed in the float bowl casing portion of said primary and' secondary induction passages anteriorly of the'associated throttle valves, :the secondary induction passage venturi' being disposed vertically above said primary venturi ferentially spaced above a horizontal plan through said manual throttles.

References Cited inthe file, of this patent UNITED STATES PATENTS 2,790,630 Armstrong Apr. 30, 1951 2,796,838 'Phillips' June 25, 1957 

